p.boxed
  | If Black castle long, they win. If they cannot, White wins.

p.
  Besides the usual game end conditions, White can win by preventing black
  long castle. And, Black can win by castling long.

p For example after 1.e4 e5 2.Bc4, Nc6?? loses immediatly: 3.Bxf7+

figure.diagram-container
  .diagram
    | fen:r1bqkbnr/pppp1Bpp/2n5/4p3/4P3/8/PPPP1PPP/RNBQK1NR:
  figcaption After 1.e4 e5 2.Bc4 Nc6 3.Bxf7+ 1-0

h3 Source

p
  a(href="https://www.chessvariants.com/winning.dir/castle.html")
    | Castle chess
  |  on chessvariants.com. See also 
  a(href="http://cinquantesignes.blogspot.com/2020/09/castlechess.html")
    | this post
  |  giving some clarifications and advices.

p Inventor: Éric Angelini (1996)